Previous work has shown that the extracellular matrix (ECM) within peripheral nerves affects the behavior of the peripheral glial cell, the Schwann cell (SC), and that if ECM assembly is prevented normal SC development (i.e. ensheathment and myelination of axons) does not occur. It has also been shown that SCs themselves synthesize the components of this ECM, in particular the basal lamina that surrounds each SC-axon unit. Neurons, however, appear to regulate ECM formation, in that this ECM is assembled only in the presence of neurons. This matrix is known to contain collagen (types I, III, IV and V), laminin, and fibronectin. The long range goals of this project are to understand: 1) how the ECM affects SC behavior; and 2) how the elaboration of the peripheral nerve ECM is regulated. As steps toward achieving these goals the specific aims of this proposal are to: 1) determine whether and what kinds of proteoglycans (PGs) and glycosaminoglycans (GAGs) are synthesized by SCs and/or peripheral neurons; and 2) clarify the role of neurons in regulating peripheral nerve ECM formation. These experiments will utilize primary cultures of embryonic rat SCs and sensory neurons which fully express their normal developmental capabilities, including axonal growth, axon-stimulated SC proliferation, ECM formation, and ensheathment and myelination of axons by SCs. Proteoglycans synthesis will be measured by applying established biochemical methods for PG and GAG analysis to material obtained frm metabolically labeled cultured cells grown under a variety of conditions. Previous results on the role of neurons in ECM formation have suggested that neurons regulate ECM formation by modulating the amounts of type IV collagen secreted by SCs. The effect of neurons on ECM formation will be further analyzed by: 1) measuring biochemically the synthesis and turnover rates of specific ECM components made by SCs in the presence and absence of neurons; 2) determining whether SCs produce a type IV specific collagenolytic activity; and 3) measuring by in vitro translation the amounts of specific nRNAs for ECM macromolecules in SCs grown in the presence and absence of neurons.